Bug 16569 – Assertion failure on splitter.back on empty string

import std.stdio; import std.algorithm; import std.range; import std.string; void main() { string str = ""; writeln( splitter(str, '.').back ); } core.exception.AssertError@std/algorithm/iteration.d(3132): Assertion failure ---------------- ??:? _d_assert [0x43dd1f] ??:? void std.algorithm.iteration.__assert(int) [0x4432b0] ??:? pure @property @safe immutable(char)[] std.algorithm.iteration.splitter!("a == b", immutable(char)[], char).splitter(immutable(char)[], char).Result.back() [0x43b8d6] ??:? _Dmain [0x43ae41] ??:? _D2rt6dmain211_d_run_mainUiPPaPUAAaZiZ6runAllMFZ9__lambda1MFZv [0x43e33e] ??:? void rt.dmain2._d_run_main(int, char**, extern (C) int function(char[][])*).tryExec(scope void delegate()) [0x43e288] ??:? void rt.dmain2._d_run_main(int, char**, extern (C) int function(char[][])*).runAll() [0x43e2fa] ??:? void rt.dmain2._d_run_main(int, char**, extern (C) int function(char[][])*).tryExec(scope void delegate()) [0x43e288] ??:? _d_run_main [0x43e1f9] ??:? main [0x43d049]

It's not a bug. splitter returns a range, in your case this range is empty. The way of iterating/using a range is always to test for emptiness before using front/back or popFront/Back: auto rng = str.splitter('.'); if (!rng.empty) writeln(rng.back);